This proposal focuses on the application of pericyclic reactions in new methodology for the synthesis of several important classes of organic compounds. Part I describes the further development of a general regiocontrolled annulation route to highly substituted aromatic and heteroaromatic compounds. The application of this methodology to the total synthesis of biologically active natural products will be investigated; specific target compounds include the aegyptinone antibiotics, eight related diterpenoid quinones isolated from the important Chinese drug Dan Shen, the antibiotic phenalenone diterpenes salvilenone and atrovenetin, the antihypertensive diterpene barbatusol, the antineoplastic diterpene taxmairin B, and the mitomycin antitumor antibiotics. Part II of the proposal describes a general strategy for the synthesis of alkynylketenes, a class of ketene derivatives which are at present almost completely unknown. The application of the electrocyclization of certain conjugated alkynylketenes will be investigated as a method for the synthesis of aromatic compounds and as a means of generating certain novel aromatic diradical species.